Incorporation of CC steps into Z-DNA: interplay between B-Z junction and Z-DNA helical formation.

Published

Journal Article

The left-handed DNA structure, Z-DNA, is believed to play important roles in gene expression and regulation. Z-DNA forms sequence-specifically with a preference for sequences rich in pyrimidine/purine dinucleotide steps. In vivo, Z-DNA is generated in the presence of negative supercoiling or upon binding proteins that absorb the high energetic cost of the B-to-Z transition, including the creation of distorted junctions between B-DNA and Z-DNA. To date, the sequence preferences for the B-to-Z transition have primarily been studied in the context of sequence repeats lacking B-Z junctions. Here, we develop a method for characterizing sequence-specific preferences for Z-DNA formation and B-Z junction localization within heterogeneous DNA duplexes that is based on combining 2-aminopurine fluorescence measurements with a new quantitative application of circular dichroism spectroscopy for determining the fraction of B- versus Z-DNA. Using this approach, we show that at least three consecutive CC dinucleotide steps, traditionally thought to disfavor Z-DNA, can be incorporated within heterogeneous Z-DNA containing B-Z junctions upon binding to the Zα domain of the RNA adenosine deaminase protein. Our results indicate that the incorporation of CC steps into Z-DNA is driven by favorable sequence-specific Z-Z and B-Z stacking interactions as well as by sequence-specific energetics that localize the distorted B-Z junction at flexible sites. Together, our results expose higher-order complexities in the Z-DNA code within heterogeneous sequences and suggest that Z-DNA can in principle propagate into a wider range of genomic sequence elements than previously thought.

Full Text

Duke Authors

Cited Authors

  • Bothe, JR; Lowenhaupt, K; Al-Hashimi, HM

Published Date

  • August 28, 2012

Published In

Volume / Issue

  • 51 / 34

Start / End Page

  • 6871 - 6879

PubMed ID

  • 22873788

Pubmed Central ID

  • 22873788

Electronic International Standard Serial Number (EISSN)

  • 1520-4995

Digital Object Identifier (DOI)

  • 10.1021/bi300785b

Language

  • eng

Conference Location

  • United States